A reassessment of lake and wetland feedbacks on the North African Holocene climate

Abstract

Large parts of the Sahara were vegetated during the early to mid Holocene. Several positive feedbacks, most notably related to vegetation, have been shown to have favored the northward migration of the desert boundary. During this period, numerous lakes and wetlands existed in the Sahara region and might have acted as a local moisture source. However, earlier model studies of the effects of open water surfaces on the mid‐Holocene North African climate suggested that these were weak and did not contribute significantly to this northward migration of the North African climate zones. Using a state‐of‐the‐art climate model, we suggest that the effect of open‐water surfaces on the mid‐Holocene North African climate might have been much stronger than previously estimated, regionally more than doubling the simulated precipitation rates. It is thus possible that this effect, combined to other known positive feedbacks, favored the appearance of the “Green Sahara”.